Adamantyl containing intermediates

ABSTRACT

A group of adamantyl containing intermediates is useful to prepare certain oligopeptides which improve kidney function. A representative species of this group is N-(1-adamantyl)-ethanoylproline.

This is a divisional application of U.S. Ser. No. 350,975 filed Feb. 22,1982, now U.S. Pat. No. 4,387,049.

This invention comprises a new group of chemical compounds whosestructures have a prolyl-phenylalanine nuclear skeleton with acharacterizing adamantyl-lower alkanoyl substituent on the N-member ofthe prolyl ring. The utility of the compounds is to improve kidneyfunction and thereby to lower abnormal blood pressure if present.

DESCRIPTION OF THE ART

Belgian Pat. No. 830,911 describes a series ofprolyl-phenylalanyl-arginine tripeptides having a ω-phenylpropionyl atthe proline ring nitrogen and an aromatic substituent at the otherterminal amino group which are useful in certain analytical procedures.Certain tripeptides alleged to have bradykinin inhibitory activityincluding prolyl-phenylalanyl-arginine chains are described in PCTspecification I.P. No. W080/00252. DT No. 2,943,582 discloses a numberof prolyl-phenylalanyl-arginine tripeptides as the naphthyl estersuseful as substrates for various enzymes. The present invention iscomprised of compounds whose structures differ from those in the priorart as well as from those of my prior inventions in the criticaladamantyl-alkanoyl substituent.

DESCRIPTION OF THE INVENTION

The new chemical compounds of this invention have structures which aredistinguished by having a prolyl-α-lower alkylphenylalanine dipeptidechain substituted at the ring N-member of the proline ring with a1-adamantyl alkanoyl group and at the carboxy terminus via the aminogroup of the alanylamide structure with α-carboxy-ω-guanidinobutyl,ω-guanidino-alkyl, ω-aminoalkyl or ω-carboxyalkyl fragments. Thecritical structural feature of these compounds is the 1-adamantyl-loweralkanoyl portion of the compounds. The adamantyl group is systematicallynamed tricyclo(3.3.1.1³.7)decanyl. Said adamantyl group may also have ahydroxy substituent at the methylene or bridgehead carbon member.

Exemplary of the compounds of this invention are those represented byFormula I: ##STR1## in which:

R is ##STR2## ω-aminoalkylamino (--NH--(CH₂)_(m) --NH₂) orω-carboxyalkylamino (--NH--(CH₂)_(m) --CO₂ H);

R¹ or R² each represent hydrogen, methoxy or hydroxy;

R³ is hydrogen or lower alkyl of 1-3 carbons especially methyl;

n is an integer from 1-3; and

m is an integer of from 2-6.

A subgeneric group of new compounds of this invention are those ofFormula I in which R is arginyl. A second group are those in which R isarginyl, R¹ and R² are each hydroxy or methoxy and n is 1. As statedabove R³ is preferably methyl and n is 1.

Also included in this invention are the pharmaceutically acceptable acidaddition or alkali metal salts of the compounds of Formula I. Examplesof these are the salts prepared by reacting the peptide bases withsuitable acids, for example hydrochloric acid, sulfuric acid, sulfamicacid, phosphoric acid, acetic acid, maleic acid, methane sulfonic acidor hydrobromic acid together with the sodium, potassium or calcium saltsif a peptide acid is reacted with a base or metal. Such salts areprepared by methods known to the art.

The compounds of this invention are prepared by a reaction sequencewhich involves, as a key step, formation of the amide group presentbetween the prolyl fragment and the α-alkylphenylalanyl fragment usingstandard peptide coupling methods. The overall sequence of peptideformation can also be reversed which sequence may even be preferred if Rin Formula I contains a basic or acid center rather than a protectedgroup. ##STR3## In Reaction Sequence A, the symbols are as describedabove or protected versions thereof.

In the formation of the amide bond in Reaction Sequence A, standardpeptide coupling methods are used. Especially useful is the reaction ofthe carboxylic acid (II) with the amine (III) in the presence of adehydrating coupling agent such as dicyclohexylcarbodiimide in asuitable organic solvent such as tetrahydrofuran, dimethylacetamide ordimethylformamide at moderate temperatures, such as room temperature,until reaction is complete usually from 1-12 or more hours.

In the Reaction Sequence A, n, m, R, R¹, R² and R³ are as defined aboveor are precursor groups on intermediate compounds. The latter may be anester, ether, nitro or benzyl derivative which generates the desired endor even another intermediate product after regenerative hydrolytic orhydrogenation reactions. The new compounds of Formula II are valuableintermediates and a part of this invention.

The compounds of this invention have pharmacodynamic activity and assuch are useful ingredients for pharmaceutical dosage units or methods.More specifically they increase renal blood flow and decrease renalvascular resistance as does dopamine. Their effect in improving kidneyfunction appears to be cumulative. These compounds, therefore, are longacting renal improvement or anti-hypertensive agents.

The biological activity of the compounds of Formula I was demonstratedby administering the compounds by infusion to anesthetized dogsmeasuring the mean arterial blood pressure, renal blood flow, renalvascular resistance and heart rate in the test procedure explained indetail in U.S. Pat. No. 4,197,297. Generally speaking the compounds gavea decreased renal vascular resistance and/or increased renal blood flowat doses ranging from 1/10 to 1/100 that for dopamine.

One skilled in the art will recognize that the compounds of thisinvention may exist in various configurations such as optical isomers ormixtures thereof. Such compounds are easily prepared by substituting thedesired amino acids of chosen configuration into the chemical reactionsof the examples which illustrates this invention. Also the proline ringin the compounds of Formula I may be replaced by other prolyl-likefragments such as dehydroprolyl

The following examples are intended to teach the preparation and use ofthe new compounds of this invention but not to limit its scope. Alltemperatures are expressed in degrees Centigrade.

EXAMPLE 1

A mixture of 4.8 g (0.02 m) of L-proline benzyl ester hydrochloride,3.88 g (0.02 m) of α-(1-adamantyl)acetic acid, 5.4 g (0.04 m) of1-hydroxybenzotriazole, 2.56 ml of N-ethylmorpholine, 60 ml ofdimethylformamide and 4.16 g (0.02 m) of dicyclohexylcarbodiimide wasstirred overnight at 25°. The mixture was filtered and thetetrahydrofuran removed in vacuo from the filtrate to leave a residuewhich was taken up in 200 ml of ethyl acetate. The resulting extract wasacidified with dilute hydrochloride acid. The layers were separated. Theorganic layer was extracted several times with ethyl acetate. Theorganic extracts were combined and washed with dilute acid, water,bicarbonate solution and brine then dried and evaporated to give anamber syrup of N-(1-adamantyl)-ethanoylproline benzyl ester, m/e=381. Asecond run on a 0.04 m scale gave 16.2 g of ester.

This material (16.2 g, 0.043 m) was dissolved in 85 ml of ethyl alcoholand hydrogenated using standard low pressure conditions over 2.5 g of10% palladium-on-charcoal. The mixture was filtered and the filtrateevaporated to give 7.9 g (64%) of the desired free acid, m.p. 176°-178°,[α]_(D) ²⁵ =-51.3° (c 1, methanol).

Anal. Calcd. for C₁₇ H₂₅ NO₃ : C, 70.07; H, 8.65; N, 4.61. Found C,69.99; H, 8.72; N, 4.67.

A mixture of 6.4 g (0.0358 m) of D,L-α-methylphenylalanine, 9.38 g(0.043 m) of di-tert.-butyldicarbonate, 5.0 ml of triethylamine and 100ml of dimethylformamide was stirred 20 hours at room temperature. Themixture was filtered. The filtrate was evaporated to give a residuewhich was taken up in ethyl acetate. The extract was washed with water,cold 1 N hydrochloric acid and water. The dried organic extract wasevaporated to give a syrup which solidified and was crystallized fromhexane-ether, 4.6 g (46%) ofN-tert.-butoxycarbonyl-D,L-α-methylphenylalanine, m.p. 134°-135°.

This t.-boc material (4.4 g, 0.016 m) was suspended in drytetrahydrofuran and reacted with 4.94 g of dicyclohexylcarbodiimide, 4.3g of ω-nitro-L-arginine, methyl ester hydrochloride, 4.32 g of1-hydroxybenzothiazole and 2.76 g of N-ethylmorpholine at 0° for 1 hourthen at room temperature for 72 hours. Working up as above gave 6.8 g(86%) ofN-tert.-butoxycarbonyl-D,L-α-methylphenylalanyl-α-nitro-L-argininemethyl ester, m.p. 143°-145°. [α]_(D) ²⁵ (c 1, CH₃ OH)=-33.9°.

Anal. Calcd. for C₂₂ H₃₄ N₆ O₇ : C, 53.43; H, 6.93; N, 16.99. Found: C,53.09; H, 6.82; N, 16.61.

This t.-boc 23.0 g (46.6 mm) and 9.2 ml (70 mm) of m-methoxyanisole weresuspended in methylene chloride at 0°. After 15 minutes stirring, themixture was evaporated and ethereal hydrogen chloride added. Theseparated solid was dissolved in water and washed with ether. Theaqueous layer was evaporated under vacuo to give 13.5 g (67%) ofD,L-α-methylphenylalanyl-ω-nitro-L-arginine, methyl ester,hydrochloride, [α]_(D) ²⁵ (c 1, H₂ O)=-32.8°.

Anal. Calcd. for C₁₇ H₂₆ N₆ O₅.HCl.1/2H₂ O 1/2C₂ H₅ OH: C, 46.70; H,6.75; N, 18.15. Found: C, 46.32; H, 6.72; N, 18.11.

A mixture of 1.4 g (4.8 mm) of the adamantyl compound and 2.1 g (4.9 mm)of the arginine compound with the coupling reagents mentioned above instoichiometric quantities in 30 ml of tetrahydrofuran and 5 ml ofdimethylformamide was reacted at room temperature for 72 hours. Thereaction mixture was filtered and evaporated. The residue was washed asabove then passed over a column of 60 g of silica gel usingmethanol-methylene chloride to give 9 g (28%) ofN-(1-adamantyl)-ethanoyl-L-proline-D,L-α-methylphenylalanyl-α-nitro-L-argininemethyl ester, [α]_(D) ²⁵ =-78.7° (c 0.5, CH₃ OH).

A mixture of 0.9 g (1.3 mm) of the ester, 15 ml of methanol and 2 ml of2.5 N sodium hydroxide solution was stirred overnight. The methanol wasremoved and water added to the residue. Concentrated hydrochloric acidwas added slowly to separate 0.8 g (94%) of the free acid.

This material (0.8 g, 1.2 mm) was dissolved in 25 ml of 1:1ethanol-acetic acid solution then added to a slurry of 1.3 g ofpalladium-on-barium sulfate in ethanol. After hydrogenation for 6 hoursat moderate pressure twice with fresh catalyst, the mixture wasfiltered. The filtrate was evaporated. The residue was dissolved inmethanol and passed over 20 g of silica gel to give 170 mg (23%) of thedesiredN-(1-adamantyl)-ethanoyl-L-prolyl-D,L-α-methylphenylalanyl-L-argininehydrate, [α]_(D) ²⁵ =+66.8° (c 1, H₂ O).

Anal. Calcd. for C₃₃ H₄₈ N₆ O₅.H₂ O: C, 63.24; H, 8.04; N, 13.41. Found:C, 62.95; H, 8.09; N, 13.40.

This compound in the renal vasodilator protocol in anesthetized dogs byinfusion gave an ED₁₅ of 72 μg/kg., dopamine gave an ED₁₅ of 3.5 μg/kg.

Substituting D-proline, benzyl ester hydrochloride in this proceduregives the corresponding isomer.

EXAMPLE 2

The N-acylproline (2.9 g, 0.01 m) from Example 1 is mixed with 2.9 g(0.01 m) of D,L-α-methyl-3,4-dimethoxyphenylalanine methyl esterhydrochloride, 2.7 g (0.02 m) of 1-hydroxybenzotriazole, 2.0 ml ofN-ethylmorpholine, 2.06 g (0.01 m) of dicyclohexylcarbodiimide, 20 ml ofdimethylformamide and 40 ml of tetrahydrofuran. The mixture is stirredat room temperature for 72 hours.

The reaction mixture is filtered. The filtrate is concentrated. Theresidue is taken up in ethyl acetate and washed with dilute acid, water,bicarbonate and brine. The organic extract is dried and evaporated togive 5.12 g ofN-(1-adamantyl)-ethanoyl-L-prolyl-D,L-α-methyl-3,4-dimethoxyphenylalaninemethyl ester.

The ester dipeptide (5.2 g), 45 ml of methyl alcohol and 2.5 ml of 2.5 Nsodium hydroxide solution are mixed and stirred for 17 hours. Themethanol is taken off and the residue taken up in water and filtered.The aqueous solution is acidified with conc. hydrochloric acid to give asolid which is taken into methylene chloride. After washing with water,the methylene chloride extract is dried and evaporated to give 3.2 g ofthe desired dipeptide intermediate as the free acid.

Dicyclohexylcarbodiimide (1.28 g, 6.2 mm) is added to a mixture of 3.2 gof the dipeptide acid, 1.67 g of ω-nitro-L-arginine, methyl ester,hydrochloride, 1.68 g of 1-hydroxybenzotriazole, 3.0 ml ofN-ethylmorpholine, 10 ml of dimethylformamide and 30 ml of drytetrahydrofuran. The resulting mixture is stirred at room temperaturefor 54 hours. The mixture is filtered and the filtrate diluted with icedbrine, dilute hydrochloric acid and ethyl acetate. The separated organicextract is washed as above, dried and evaporated to give(1-adamantyl)-ethanoyl-L-prolyl-D,L-α-methyl-3,4-dimethoxyphenylalanyl-ω-nitro-L-argininemethyl ester.

This material (3.7 g) is stirred in 60 ml of methyl alcohol and 20 ml of2.5 N sodium hydroxide solution at 25° for 17 hours. The alcohol isevaporated off. The residue is suspended in water and filtered. Thefiltrate is acidified with concentrated hydrochloric acid to give aresidue which is dissolved in ethyl acetate-methanol. The extract iswashed with brine, dried and evaporated to give the desired acid.

A mixture of 1.8 of this ω-nitro-tripeptide acid, 2.5 g of 10%palladium-on-barium sulfate, 50 ml of ethyl alcohol and 30 ml of glacialacetic acid is hydrogenated at low pressure as described above. Thecatalyst is removed and the hydrogenation solution is evaporated. Theresidue is recrystallized to giveN-(1-adamantyl)-ethanoyl-L-prolyl-D,L-α-methyl-3,4-dimethoxyphenylalanyl-L-arginineacetic acid salt.

EXAMPLE 3

A mixture of 2.7 g ofN-(1-adamantyl)-propionyl-L-prolyl-D,L-α-methyl-3,4-dimethoxyphenylalanine,prepared as described in Example 2, 1.22 g of 1-hydroxybenzotriazole,1.0 g of N-carbobenzyloxy-1,3-diaminopropane, 4 ml of N-ethylmorpholine,0.93 g of dicyclohexylcarbodiimide, 30 ml of dry tetrahydrofuran and 10ml of dimethylformamide is stirred at ambient temperature for 72 hours.The product is isolated as in Example 1 to give the carbobenzoxydipeptide which is taken over a silica gel column.

This material, 1.6 g, is hydrogenated at low pressure (55 p.s.i.) with2.0 g of 10% palladium-on-charcoal in 60 ml of ethanol and 20 ml ofglacial acetic acid. The filtered mixture is then concentrated. Theresidue is taken up in ethanol and acidified with ethereal hydrogenchloride to giveN-(1-adamantyl)-propionyl-L-prolyl-D,L-α-methyl-3,4-dimethoxyphenylalanine-3-aminopropylamidehydrochloride.

EXAMPLE 4

N-(1-Adamantyl)-ethanoyl-L-proline (2.8 g) is reacted with 2.46 g ofD,L-α-methyltyrosine, methyl ester, hydrochloride by thedicyclohexylcarbodiimide route of Example 1 to giveN-(1-adamantyl)-ethanoyl-L-prolyl-D,L-α-methyltyrosine, methyl ester.This material (4.9 g) is hydrolyzed in alcoholic alkali to give thedesired intermediate acid. This material (4.0 g) is reacted with 2.34 gof ω-nitro-L-arginine, methyl ester, hydrochloride as above to give,after hydrolysis and reduction,N-(1-adamantyl)-propionyl-L-prolyl-D,L-α-methyltyrosyl-L-arginine as theacetic acid salt.

EXAMPLE 5

A mixture of 10 mmoles ofN-(1-adamantyl)-butyryl-L-prolyl-D,L-α-methyl-4-methoxyphenylalanineprepared as in Example 2, 10 mm of 3-aminopropylguanidine dihydrobromide(Chem. Abst. 23, 1880), 20 mm of 1-hydroxybenzotriazole, 8 ml ofN-ethylmorpholine, 10 mm of dicyclohexylcarbodiimide, 30 ml of drytetrahydrofuran and 20 ml of dimethylformamide is stirred at 25° for 18hours. After filtration, the filtrate is evaporated. The residue isdissolved in ethyl acetate. The extract is washed with 3% aqueous aceticacid, water and 5% sodium bicarbonate solution. The dried concentratedresidue is dissolved in methyl alcohol and added dropwise to 5:1ether-petroleum ether to giveN-(1-adamantyl)-butyryl-L-prolyl-D,L-α-methyl-4-methoxyphenylalanine3-guanidinopropylamide as an amorphous solid.

N-(1-Adamantyl)-ethanoyl-prolyl-D,L-α-ethyl-4-methoxyphenylalanine-3-guanidinopropylamideis prepared in like fashion. Also using the condensation method ofExample 3 but substituting a stoichiometric quantity of methylω-aminocaproate to give the methyl ester derivative of the peptidefollowed by saponification using sodium hydroxide-methanol as in Example2 givesN-(1-adamantyl)-propionyl-L-prolyl-D,L-α-methyl-3,4-dimethoxyphenylalanine-ω-carboxypentylamide.

The new chemical compounds described above are incorporated into dosageunit forms and used in methods for improving renal function, treatinghigh blood pressure or treating shock using standard methods asdisclosed in the above referenced U.S. Pat. No. 4,197,297 at line 19column 6 to line 48 column 7 as well as Examples 8 and 9. The doses ofthe present compounds in the pharmaceutical dosage unit will be aneffective nontoxic quantity selected from 50-500 mg of active base,preferably 75-250 mg. These are administered to patients in need oftreatment for the noted clinical conditions from 1-5 times daily.

What is claimed is:
 1. A chemical compound of the structural formula:##STR5## in which n is an integer of 1-3.
 2. The chemical compound ofclaim 1 being N-(1-adamantyl)-ethanoylproline.